Tumor cell-derived TGF-β and IL-10 dysregulate paclitaxel-induced macrophage activation

Abstract

Paclitaxel (TAXOL™) activates in vitro macrophage (Mø) expression of proinflammatory and cytotoxic mediators, including IL-12, tumor necrosis factor α (TNF-α), and nitric oxide (NO). However, tumors dysregulate Mø through soluble suppressor molecules, and it is possible that tumors evade paclitaxel-mediated immune effector function through the production of immunomodulatory molecules and inhibition of Mø function in situ. Because Mø activation in the tumor microenvironment is a desirable goal of anti-tumor immunotherapy, we evaluated whether tumor-derived immunomodulatory factors dysregulate paclitaxel-mediated Mø activation. Tumor cell-derived supernatant suppressed paclitaxel's capacity to induce IL-12, TNF-α, and NO production by RAW264.7 Mø. Tumor factors also dysregulated paclitaxel-induced expression of a HIV-LTR, promoter-driven luciferase construct in RAW264.7 Mø, suggesting that tumors may inhibit a broad range of Mø functionality. Depletion studies revealed that IL-10 and transforming growth factor-β1 (TGF-β1), but not prostaglandin E2 (PGE2), impaired paclitaxel-mediated activation, suggesting that abrogation of these factors in situ might restore paclitaxel's activating capacity and enhance anti-tumor efficacy.